1. Field of the Invention
The present invention relates to removal of ringing in the input unit of a pin electronics card used in semiconductor testing apparatus, output stage circuit inside the IC or LSI, or output unit of a device under test board (DUT board) used in semiconductor testing apparatus, and more particularly to a ringing preventive circuit for removing noise such as ringing from a transmission path in which an electric signal is transmitted.
2. Description of the Background Art
FIG. 25 is a conceptual diagram showing the connected state of the DUT board mounting a semiconductor device such as IC and LSI, and the input unit of a pin electronics card of a semiconductor testing apparatus, for testing a semiconductor apparatus such as IC and LSI. In FIG. 25, reference numeral 1 denotes an objective device to be tested such as IC and LSI, 2 is a DUT board for mounting the objective device 1, 3 is a holder such as socket and prober fixed on the DUT board 2 for holding and electrically connecting the objective device 1, 4 is a transmission path for transmitting an electric signal outputted from the output unit of the objective device 1, being connected to the objective device 1 in the holder 3, 5 is a connector connected to the transmission path 4 provided at the DUT board 2 side, 6 is a semiconductor testing apparatus for testing the objective device 1,7 is a pin electronics card provided in the semiconductor testing apparatus 6 and including a comparator or the like, and 8 is a connector provided in a pin electronics card 7 to be connected to the connector 5 of the DUT board 2.
The pin electronics card 7 of the semiconductor testing apparatus 6 is an input and output interface with the objective device 1, and has a significant influence on the test performance.
FIG. 26 is a circuit diagram showing the outline of the structure of the pin electronics card 7 of the semiconductor testing apparatus shown in FIG. 25. In FIG. 26, reference numeral K1 is a relay having one end connected to the connector 8 for making or breaking a connection between the one end and the other end in response to a control signal, 11 is a pin electronics comparator having an input terminal 11a connected to the other end of the relay K1, a terminal connected to a power source E5 to be provided with a reference voltage V.sub.Hth, a terminal connected to a power source E6 to be provided with a reference voltage V.sub.Lth, and an output terminal 11b for outputting the result of comparison of the voltage at the input terminal 11a with the reference voltages V.sub.Hth, V.sub.Lth, 12 is a pin electronics driver having an input terminal 12a for receiving a signal to be given to the objective device for testing, and an output terminal 12b connected to the other end of the relay K1, and 13 is a pin electronics control circuit for processing the signal to be given to the objective device from the semiconductor testing apparatus to give to the input terminal 12a of the pin electronics driver 12, processing the signal outputted from the output terminal 11b of the pin electronics comparator 11 to be taken into the semiconductor testing apparatus, and controlling to open or close the relay K1. Herein, it is supposed that reference voltage V.sub.Hth &gt;reference voltage V.sub.Lth.
The operation of the conventional semiconductor testing apparatus shown in FIG. 25 and FIG. 26 is described below. In particular, processing of the signal to be outputted from the objective device 1 is explained. In the pin electronics card 7, in order to process an input signal, the relay K1 is in ON (closed) state, so that the pin electronics comparator 11 may be connected between the connector 8 and pin electronics control circuit 13. The voltage V.sub.CO at the output terminal 11b of the pin electronics comparator 11 is, supposing the voltage at the input terminal 11a of the pin electronics comparator 11 to be V.sub.Ci, V.sub.CO =V.sub.CL when V.sub.Ci &gt;V.sub.Hth, V.sub.CO =V.sub.CL when V.sub.Ci &lt;V.sub.Lth, and V.sub.CO =V.sub.CH when V.sub.Lth &lt;V.sub.Ci &lt;V.sub.Hth, where voltage V.sub.CL is the lower side logic level in the pin electronic control circuit 13, and voltage V.sub.CH is the higher side logic level in the pin electronics control circuit 13.
FIG. 27 is a waveform diagram showing the signal processed by the pin electronics card and the processing result in the pin electronics comparator. The waveform shown in (a) of FIG. 27 is a voltage waveform of an ideal electric signal suited to processing of the pin electronics comparator 11. Ideally, from the output circuit of the objective device 1 shown in FIG. 25, a signal having a waveform as shown in (a) of FIG. 27 is outputted, and passes through the transmission path 4, and a signal having the waveform shown in (a) of FIG. 27 is put into the connector 8 of the pin electronics card 7 in the semiconductor testing apparatus 6. From the connector 8 which is the input and output terminal of the pin electronics card, an ideal signal Vi is put in, and it is supplied into the pin electronics comparator 11 through the relay K1. Therefore, the voltage V.sub.Ci at the input terminal 11a of the pin electronics comparator is ideally a signal Vi having the waveform shown in (a) of FIG. 27. At this time, the output impedance of the pin electronics driver 12 is supposed to be in high impedance state (hereinafter called Hi-Z state). Hence, ideally, the voltage waveform generated at the output terminal 11b by the action of the pin electronics comparator 11 is as shown in (b) of FIG. 27.
Actually, however, in the process of the waveform passing through the transmission path 4 and others, the signal having the voltage waveform as shown in FIG. 28 mixed with ringing and other noise due to inductance component and capacitance component of the transmission path 4, impedance mismatching of the transmission path 4, incoming noise mixed in the transmission path 4 and others is put into the pin electronics comparator 11.
FIG. 28 is a waveform diagram showing the signal processed in the pin electronics card and the processing result in the pin electronics comparator. When a signal having the waveform as shown in (a) of FIG. 28 is put into the pin electronics comparator 11, the pin electronics comparator 11 may sometimes malfunction. When the waveform shown in (a) of FIG. 28 is put into the pin electronics comparator 11, malfunction occurs in the portion crossing the voltage V.sub.Hth in shaded region B in (a) of FIG. 28, and in the portion crossing the voltage V.sub.Lth in shaded region D. When the signal having the waveform shown in (a) of FIG. 28 is put into the pin electronics comparator 11, the waveform appearing at the output terminal 11b of the pin electronics comparator 11 is as shown in (b) of FIG. 28. Shaded region E in (b) of FIG. 28 is the malfunctioning portion.
The pin electronics card is an interface between the objective device 1 and semiconductor testing apparatus 6, and the information indicated by the signal outputted from the objective device 1 must be accurately communicated to the semiconductor testing apparatus 6, but this object may not be achieved if malfunction occurs in the pin electronics comparator 11.
Incidentally, transmission of pulse signal or processing is not limited to the semiconductor testing apparatus alone, but such scene is often encountered in general semiconductor devices. FIG. 29 is a conceptual diagram showing part of the constitution of a general semiconductor device. In FIG. 29, reference numeral 14 is a semiconductor device, 15 is an output pin of the semiconductor device 14, 16 is an output buffer connected to the output pin 15 for giving an output signal to the output pin 15, 17 is a transmission path connected to the output buffer 16, and 18 is a circuit before an output stage for generating a circuit to be transmitted through the transmission path 17. The transmission path 17 may contain wiring of aluminum, polysilicon or the like, in the semiconductor device 14, and the output pin 15 may be a pad or the like.
A pulse signal having a certain waveform is outputted from the circuit before an output stage 18, and is transmitted to the output buffer 16 through the transmission path 17. It is further transmitted from the output buffer 16 having a low output impedance to the output pin 15, and is outputted outside the semiconductor device from the output pin 15. The waveform of the signal outputted from the circuit before an output stage 18 and the waveform transmitted to the output pin 15 should be ideally ringing-free waveform as shown in (a) of FIG. 27.
However, for example, when a signal having a waveform as shown in (a) of FIG. 27 is outputted from the circuit before an output stage 18, in the process of passing through the transmission path 17 or output buffer 16, it may be changed to a waveform having noise such as ringing, as shown in (a) of FIG. 28, due to inductance component in the transmission path 17, crosstalk noise from the peripheral circuit or the like, and may be transmitted to the output pin 15 in such form.
The conventional semiconductor testing apparatus, DUT board, and semiconductor device are thus constituted, and ringing or other noise is caused in the process of the electric signal passing through the transmission paths 4, 17, and therefore when the signal mixed with ringing is processed, the circuit and others may malfunction, and accurate testing of semiconductor device or appropriate action of semiconductor device may not be realized.